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From Anthony Denatala

Services for Real Estate Pros with Sick Building Group, LLC

I find that it is a daily battle to educate the clients I visit on the issues related with water damage, mold growth, and poor indoor environments.  Really the list goes on and on and on and on.

If I had to make a list of the daily issues which contribute to our homes affecting our health I would begin with the simplest factor.

1: Bathroom Exhaust Fans- bathroom exhaust fans exist for a reason.....yes it can be used to vacate unwanted smells but it also acts as a reducer of humidity after lengthy showers. I find that most of my clients experiencing issues of mold do not run their exhaust fans during or even after a shower.  Humidity builds up and depending on the factors which are equal to our mold growth: small rooms with no ventilation, excess humidity, heat, organic materials for growth, differences in temperature causing walls to sweat, other areas of the home affecting our moisture levels thus increasing the humidity levels whence a fan is not used, cleanliness,.......the list can go on and on depending on various factors......

Example:  A client calls me and tells me that they can not keep tenants in a rental property they own. The tenants complain of mold related illness (respiratory, sinusitis, rashes).  The windows and walls are said to sweat and everything appears to be damp. I inspect the property to determine what may be causing these excessive conditions.  No moisture from the exterior, no signs of water damage, no leaks in the HVAC unit, condensation pump in working condition on the unit, nothing to show issues of moisture. 

Please read this:

Controversy in Physics: Crack the Window? vs The Exhaust Fan?

    When most people think of humidity, they think of something that causes nothing but distress from exhaustion, overheating, or a bad hair day, during the summer.  Yet, meteorologists get paid big bucks to test the humidity levels out there for us during all times of the year. Humidity and condensation have all types of affects on the environment.  It makes it feel hotter outside on a warm summer day, causes one to sweat a little more, and even wreaks havoc on architecture by promoting fungal growth and decay. Condensation coincides with the humidity.  It is the moisture on one's bathroom windows and mirror after a hot shower, or the drips rolling down the side of a cup of cold lemonade.  Humidity and condensation both play a huge part in my project.
    For years, meteorologists, like me during this experiment, have recorded the humidity.  Humidity is the amount of water vapor in the air and can be described in different ways. The term that one hears most often to describe the humidity is relative humidity.  To measure the relative humidity in the air, one would need a hygrometer.  There are a few different varieties, but the digital hygrometer is the most practical for this project. Another common measurement of humidity is the dew point.  The temperature, at which the moisture content in the air will saturate the air, is called the dew point. If the air is cooled further, some of the moisture will condense. Extensive research has been undertaken to discovery how humidity really affects us.  Yet the weather man isn't the only one who has been doing experiments with humidity and condensation.  Studies have been done to find the perfect storage climates for one's belongings, to help child illnesses like croup, and to see how it affects the water cycle.  As far as my project goes, there has not been a study that relates to mine. I will take this time to further explain some points of my project.

    In my experiment, I measured the relative humidity of the air in the bathroom after taking a shower.  Relative humidity is defined as "The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage" (Answers.com).  It is a little more complex than just humidity simply put.  The hygrometer is a complicated little device used only to measure relative humidity.  In a simple mechanical type of hygrometer "the sensing element is usually an organic material which expands and contracts with changes in the moisture in the surrounding air or gas" (Answers.com).  Usually, this sensing element is human hair!  I believe that the experiment I have conducted is one of great uniqueness.  I, like many other household owners I would imagine, have wondered which works better in the bathroom to rid it of steam following a shower: the handy exhaust fan, or simply opening up a window.

    Now, I am aware that simple observations of condensation levels on the window or mirror are a good indication of the humidity levels, but I wanted a precise, numbered result.  By using a Vernier hygrometer and a remote device, I was able to accurately measure the humidity levels in the bathroom following many ten-minute showers with constant temperature.  I did three separate trials that included the two variables I tested to determine which worked better to eliminate excess humidity.  I tested the efficiency of cracking the window versus using the exhaust fan.  I also included a trial where neither method was used to establish a control and a trial to determine the relative humidity of the bathroom before the experiment began; this was to highlight the natural changes of humidity from day-to-day.  The constants in this experiment are as follows: water temperature, shower length, bathroom used (square footage), and amount of time each method was in use.  I believe the results of this experiment will aid in better preventing mold growth and structural damage.


Data Analysis:
    By looking at the graphs and tables representing the data I collected for this project, it is apparent that the most effective way of getting rid of excess humidity in the bathroom is to use the exhaust fan, not by cracking the window.  In all three trials, the exhaust fan was able to reduce the humidity levels to less than those that were measured before the shower was even turned on.  That proves that the exhaust fan can efficiently reduce the amount of moisture in the air in a very short period of time.   

    The average humidity level after using the exhaust fan method was 47.5% while the average "pre-shower" humidity level was 50.2%.  Cracking the window did very little to help lower the humidity level.  The average for this method was 71.3% relative humidity.  In comparison to the constant (neither method) average of 74.6%, cracking the window is out of the question as being affective.

    Using the exhaust fan lowered the humidity level an average of 27.1% while cracking the window only lowered the humidity level an average of 3.3%.




    I was successful at accomplishing the goal of my experiment in determining which method, the exhaust fan or cracking the window, is more effective at eliminating unwanted bathroom moisture.  By using the exhaust fan, one can greatly reduce the humidity in the room, thus reducing the occurrence of many common bathroom nuisances, such as: the growth of mold and mildew, structural damage, and peeling wallpaper. 

    Another goal of this project was reached as well; a long-standing difference in opinion has finally been settled scientifically. The idea for this project came to me as a result of my father's constant complaints regarding the window being left open in the bathroom after I took a shower.  I was so certain that cracking the window was the better method.  Although it is hard for me to admit, all the data proves that my father was correct in his assumption that the exhaust fan is better, and apparently more cost efficient, as it does not affect the thermostat like opening the window does.
    The impact of my project was not wide spread, as the topic does not garner significant attention.  Mainly my own household has been impacted in a few ways.  We now all know the best way to keep our bathrooms mildew free and in great condition.  Also, our energy bills will probably be lower now that bathroom windows won't be left open causing the heat pump to work overtime. My family was also impacted negatively by the lack of hot water for their own showers during the times I was doing the experiment. 

    The main strength in this project is the Vernier devices I was able to use to collect data.  They proved to be very accurate in their measurements and allowed me to come to a firm conclusion. The only weakness I encountered was in maintaining a constant water temperature through the entire experiment.  I had to wait after many of the trials for the hot water to come back before I could go on. 

    As a result of this experiment, I observed that cracking the window in the bathroom during a shower only reduces the condensation level and not the overall humidity of the bathroom.  This surprised me as I thought that the condensation on the mirror was a good indication of the humidity being high.  I also observed that the humidity levels in the house change from day to day depending on the weather outside.  This does make sense, though I thought that the humidity was kept constant by the heat pump.

    I did not have to acquire much outside information from individuals in order to complete my project so I did not receive any feedback.  Although throughout the process my father did comment on various occasions about how he was correct in saying that the exhaust fan is more effective.

    During the research portion of this project I learned a great deal I never knew about relative humidity, condensation, and the dew point.  I am more educated in utilizing scientific probes for data collecting.  I think my patience has also improved as a result of this project.  I had to repeat the trials numerous times as I had trouble at first getting the LabPro device to work.  This extended the time it took to collect data by quite a bit as each trial took over ten minutes to complete and I had to wait for hot water to return a few times.

    I think the next step in this project would be to directly inspect the type of damage that can arise as a result of humidity in the whole house.  Mold growth and wood decay can be measured in relation to the amount of moisture present in the air.  I think this would be an interesting topic for other students to pursue.

    If I could do this project over again, I think I would test alternate ways of eliminating excess moisture, not only in the bathroom, but throughout the house.  I would look at housing insulation as well as dehumidifiers to test which has the greatest affect on humidity levels.  This would be especially informative to people who live in more tropical environments where high humidity is common year round.  In regards to my current project, I can honestly say that I would not go about it any differently as there really is not much to alter.  Although, I think I would probably repeat more trials to strengthen the accuracy of the data.


Please pass this on to your tenants, clients, homeowners, property managers, roommates, friends, relatives, whomever takes showers, lives in a home, rents, lives, and breaths, ................

This is one factor which can lead to poor indoor health.  The humidity can affect your HVAC system "the lungs of your home".  The humidity can add as a support for hidden growth associated with continued microbial growth.  However, humidity is not always bad and it is this that needs to be addressed. 

Our living conditions are exactly that...........living conditions........controlling our indoor environments is essential but moderation is the key.....as it seems with many life instances. 


I am open to all questions and even have some additional facts and solutions to share so feel free to contact me at anytime with any question. 

Anthony Denatala  







Randall Schrader
Competitive Insurance of Dundee - Dundee, FL

Wow, you work way too hard Dr. House!  It's crazy where real estate has taken us and all the things we need to think about.

Jan 06, 2009 10:35 AM